This invention relates generally to paper making machines and, more particularly, to quick connect apparatus for detachably locking a component of the headbox such, for example, as air cushion dampers, covers, bottom plates, or the like, in operative position while permitting the quick detachment thereof from the headbox to allow for cleaning or other servicing thereof.
Conventional headboxes presently in use in paper making machines may be divided into three distinct categories, namely, (1) headboxes provided with an air cushion device directly incorporated therewith or so-called air-cushion headboxes; (2) hydraulic headboxes provided with air cushion devices which are separate from the actual headbox and which are located either in the pulp stock approach pipe system upstream of the distribution header or downstream of the distribution header, and (3) hydraulic headboxes which are not equipped with such air cushion devices.
The object of providing the headbox of a paper making machine with an air cushion device is to equalize any pressure fluctuations which occur in the pulp stock flow upstream of the out flow aperture, or lip slice, of the headbox. Such pressure fluctuations are created either in the pulp stock flow system upstream of the headbox or in the course of flow of the pulp stock in the headbox itself. If these pressure fluctuations remain in the pulp stock as far as the lip slice headbox, velocity variations will occur in the rate of discharge of the stock therefrom, resulting in corresponding longitudinal variations in the base weight of the web which is subsequently formed on the forming wire of the paper machine. Since such base weight variations cannot be completely equalized during subsequent web drying steps, the same become visible in the finished paper which, of course, detracts from its value.
In order to at least partially overcome this problem, and to provide a uniform average pulp flow velocity profile, it is common practice to provide the inlet distribution pipes of the headbox, i.e., the inlet distribution header, with the shape of a truncated cone or the like in the direction transverse to the pulp stock flow, and, when desired, with a continuous by-pass flow provided at its ultimate end. A plurality of diffuser pipes extend from the conical distribution header in the longitudinal direction of pulp stock flow from which the pulp stock flows from the header into the headbox.
A serious problem exists in connection with the operation of conventional paper making machine headbox apparatus as described above. More particularly, fibers from the pulp stock tend to become caught in the flow passages of the headbox, thereby necessitating the periodic cleaning of the same at frequent intervals. These intervals depend on the particular running conditions as well as the quality of the pulp stock and vary within a very broad range. In order to allow the cleaning of headboxes in conventional paper making machines, and in particular in a machine which utilizes hydraulic headboxes, the pressure equalizing or air cushion portion located between the inlet distribution pipes or header and the turbulence section, is usually adapted to be displacable so that the distribution header and turbulence portion can be cleaned through the spaces vacated by the displaced portion, the pressure equalizing portion being easily cleaned at the same time. In such conventional headboxes, these components are generally joined at mating flanges by bolts. Thus, two joints defined by the pressure equalizing portion and the distribution header and turbulence sections are joined at respective mating flanges by bolts. For example, in a paper machine with a transverse working breath of about 8 meters, more than one hundred bolts are often used to accomplish the connection of the mating flanges. The areas in which the bolts are inserted are often extremely cramped and provide poor accessability. As a result, it is not uncommon for the detachment and reattachment of the pressure equalizing portion from the other headbox components to take between 1 and 1/2 and three hours, depending on the particular design of the machine. Of course, during this time, the paper machine is shut down thereby resulting in considerable losses in production.